This project propose to study the structure and activities of Carbohydrate-Binding Protein 35 (Mr 35,000), a lectin that binds specifically to galactose-N-acetylglucosamine (Gal-GlcNAc) containing glycoconjugates. Using a highly specific antibody directed against CBP35, we have made the striking observation that CBP35 can be found in the nucleus of a cell and that the level of expression of CBP35 and its nuclear localization may be dependent on the proliferation state of the cell. More recently, we have accumulated evidence to indicate that CBP35 is a protein associated with the core particle of the heterogeneous nuclear ribonucleoprotein complex (hnRNP). The specific objectives of the proposed research are: (a) to identify, isolate, and characterize cDNA and genomic clones for CBP35; (b) to determine the partial amino acid sequence of CBP35 at the protein level and to derive the complete amino acid sequence from the cDNA sequence; (c) to study the regulation of transcription of the CBP35 gene by Northern analysis and nuclear run-on experiments; (d) to analyze CBP35 in terms of the possibility of different nuclear versus cytoplasmic forms, their relationships to the different isoelectric variants of CBP35 and the different states of phosphorylation; (e) to search for conditions that will release CBP35 from the hnRNP core particle and to identify the correspondence between CBP35 and the protein(s) of the core particle; and (f) to analyze the effect of CBP35 in certain perturbation experiments (e.g. addition of CBP35 and/or rabbit anti-CBP35) on cell free mRNA processing (splicing) systems. All of these studies should contribute to our understanding of the structure and activities of lectins endogenous to animal cells.